There are many applications where a need exists to detect pressure between two contacting surfaces, either at a single point, or at a plurality of points so as to provide a pressure profile. Such applications include detecting pressure at gaskets, seals, and other contacting surfaces in various industrial equipment for alignment, adjustment, various other set-up functions, testing, maintenance, and the like; in research facilities for measurement and testing of various products; and in medical facilities for measuring and testing such things as foot pressure distribution, dental occlusion and the like. While pressure sensors for certain of these applications are fabricated as a matrix array, many of these applications require only one or more button sensors, the output or outputs from which are read locally, are fed to a computer, either directly or indirectly, or are otherwise utilized.
In order to achieve optimum sensitivity for a given application, it is desirable that the sensor utilized be selected so as to function optimally in the pressure range being measured. Thus, where the pressure range over which measurements are being taken is small, and detection of small pressure changes is desired, high sensitivity sensors are required; while where the pressure range extends over many pounds or kilograms, sensitivity at the ounce or gram level may be more than adequate. Further, while the sensor elements interposed between the contacting surfaces for which pressure is being measured are high wear items which may only be suitable for a single test or a small number of tests, the remainder of the equipment may have an extended lifetime. Therefore, it is desirable to design sensor equipment with low-cost, flexible pressure sensor assemblies having various configurations and sensitivities which can be easily inserted and removed from a handle which may be connected directly or indirectly to a computer receiving the measurements, or may otherwise output the measurements. While the handle is generally little more than a connector to the pressure sensor assembly, it may, in some applications, also contain selected circuitry. For example, since the output from the sensors may be at relatively low voltage and/or current, the handles for the sensor assembles may contain amplifiers for such signals. Further, since analog output signals are subject to distortion, such handles may also contain converters for changing analog outputs from the sensors to digital signals applied to the computer and for converting digital control signals from the computer to analog. For example, the computer may control the test voltage applied to the sensor(s) to control sensitivity.
One problem with such handles is assuring that the sensor is properly seated in the handle before measurements are taken, since improper seating of the sensor in the handle can result in either erroneous readings being taken or in a loss of data which may be difficult to subsequently reconstruct. Two factors contribute to and insure proper seating has occurred before measurements are taken. The first factor is to design the sensor and handle such that the sensor may be easily inserted and removed while still assuring that, when in use, sufficient pressure is applied against the sensor assembly to assure good electrical contact between its terminals and those of the handle. The second factor is to provide a simple way of detecting good electrical contact between sensor assembly and handle terminals and of providing feedback to the user or operator that good electrical contact has been established before a sensor assembly is used to take measurements. If the user does not obtain such feedback, measurements would not be taken and the sensor assembly could either be repositioned until it is properly seated, or disposed of if defective. While there are a number of sensor products of the general type indicated above currently on the market, none adequately combines ease of use with the protection factors indicated above against measurements being taken with an improperly seated sensor assembly.